Pulsation pressure decreased type pump for vehicle slip control system

ABSTRACT

The present invention provides a pulsation pressure decreased type pump. When an oil pump that is driven by a motor during the operation of an electronically controlled brake system discharges a working fluid, the working fluid passes through an annular orifice provided at a position where the working fluid is discharged and is then discharged to an outlet of a pump housing through an outflow channel formed in the orifice so as to decrease a pulsating pressure using a piston reciprocated by a cam. Therefore, it is possible to decrease a pulsating pressure generated in the pump from 20 bar to 5 bar or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on, and claims priority from, Korean Application Serial Number 10-2007-0059757, filed on Jun. 19, 2007, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a pump for a vehicle slip control system, and more particularly, to a pulsation pressure decreased type pump.

BACKGROUND OF THE INVENTION

In general, a brake of a vehicle is used to stop a vehicle or reduce the speed of a vehicle by transmitting a braking pressure, which is a hydraulic pressure, to a wheel brake on the basis of the operation of a brake pedal. Since a running vehicle is forcibly stopped by the brake, the vehicle occasionally is slipped due to the braking pressure or road conditions during braking.

A brake, which electronically controls the braking pressure of the wheel brake, has been widely used to prevent the slip from occurring. That is, there have been widely used an ABS (Anti Lock Brake System), a TCS (Traction Control System) that prevents large slip from occurring on driving wheels during quick starting and accelerating, or an ESP (Electronic Stability Program) system that minimizes a difference between an intended direction and an actual direction of a vehicle in order to safely maintain a vehicle in the intended direction under any driving conditions.

An oil pump is driven by a motor and pumps oil in the above-mentioned electronically controlled brake systems. As the pump operates, a hydraulic circuit formed between a master cylinder and a wheel cylinder controls the flow of oil in a direction toward a wheel cylinder or in a reverse direction thereof.

However, when operating, the oil pump forming the entire brake hydraulic circuit sucks or discharges the oil by a piston that is reciprocated by the motor. In particular, when the pump discharges oil, pulsation is generated at an outlet of the pump. As the piston of a valve in the pump reciprocates, a plurality of pulsation is superposed and is increased to about 20 bar, which undesirably affects related components.

SUMMARY OF THE INVENTION

Embodiments of the present invention help overcome the drawbacks of the brake system and provide a pulsation pressure decreased type pump for a vehicle slip control system that includes an orifice provided on a discharge channel of a pump that discharges a working fluid using a piston reciprocated by a cam during operation. When the pump discharges the working fluid, the orifice related with an outlet check valve controls the amount of the working fluid, so that a pulsating pressure caused by pulsation superposition is decreased from 20 bar to 5 bar or less.

Further, embodiments of the present invention provide a pulsation pressure decreased type pump including an orifice, which is formed by pressing, so as to minimize manufacturing cost and time required to manufacture and machine the orifice. The orifice decreases a pulsating pressure, which is generated at an outlet when a pump discharges a working fluid, to 5 bar or less.

Furthermore, embodiments of the present invention provide a pulsation pressure decreased type pump including an orifice, which has a discharge channel directly formed therein and is directly fixed to a sleeve. Accordingly, a discharge channel does not need to be formed in a sleeve fixed to a cap, and the sleeve does not need to be machined for the assembling of the orifice.

In addition, embodiments of the present invention provide a pulsation pressure decreased type pump including an orifice, which is provided at an outlet in a pump and directly fixed to an end of a sleeve. Accordingly, since centering between the orifice and the sleeve does not need to be performed, it is possible to easily perform assembly.

A pulsation pressure decreased type pump according to an embodiment of the present invention includes a hollow sleeve. The sleeve is fixed to a pump housing, receives a working fluid through an inflow channel formed in a radial direction, and includes a channel formed inside an end thereof opposite to the inflow channel. A piston is elastically supported in the sleeve by an inner spring. The piston is reciprocated by the drive of the pump so as to allow the working fluid to flow into an inflow channel communicating with the inflow channel of the sleeve. An inlet check valve includes a ball, a check valve spring, and a cover. The ball blocks an outlet through which the working fluid flowing into the piston passes. The check valve spring is fixed to an outlet of the piston and elastically supports the ball. The cover receives the check valve spring, is fixed to the piston, and has a radial channel serving as an outlet for the working fluid. An outlet check valve includes a ball and a check valve spring. The ball is received in a cap fixed to an end of the sleeve, and opens or closes a passage of the working fluid discharged from the sleeve. The check valve spring is inserted into the cap so as to elastically support the ball. An orifice is provided between the sleeve and the cap fixed to the end of the sleeve, and changes the flow of the working fluid discharged from the sleeve so as to decrease a pulsating pressure of the working fluid caused by the reciprocation of the piston. An outflow channel is integrally formed with the orifice so that the working fluid discharged from the sleeve through the outlet check valve is guided to an outlet of the pump housing.

In addition, the orifice may include an annular body, fixation ends, and an outflow channel. The annular body has a central hole, with which the ball of outlet check valve 8 comes in close contact, at the center thereof. The fixation ends protrude from the annular body and are fitted to a stepped orifice fixing end formed at the end of the sleeve. An outflow channel guides the working fluid which is discharged from the sleeve through the annular body, to the outlet of the pump housing.

Further, the fixation ends may be composed of an upper fixation end and a pair of left and right lower fixation ends. The upper fixation end is bent to protrude toward one side of the annular body. The pair of left and right lower fixation ends is bent to protrude toward one side of the annular body at positions corresponding to an angle of about 120° from the upper fixation end.

Furthermore, left and right divided fixation ends, which are separated from each other and face each other, may be formed by cutting a central portion of the upper fixation end so that an outflow channel for guiding the working fluid discharged from the sleeve to the outlet of the pump housing is formed in the upper fixation end.

The outflow channel may include an inlet, a narrow portion, an extension portion, and a wide portion. The inlet is formed by cutting the annular body so as to allow the working fluid to flow. The narrow portion communicates with the inlet and decreases a flow width of the working fluid to increase the flow speed of the working fluid. The extension portion forms an end of the narrow portion and has a narrow width. The wide portion expands at the end of the extension portion.

The orifice may be integrally formed by pressing.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which:

FIG. 1 is a view showing the structure of a pulsation pressure decreased type pump for a vehicle slip control system according to an embodiment of the present invention; and

FIGS. 2A and 2B are working fluid flow diagrams of the pulsation pressure decreased type pump according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a view showing the structure of a pulsating pressure decreased type control valve for a vehicle slip control system according to an embodiment of the present invention. An oil control pump, which pumps and circulates oil used as a working fluid, of an electronically controlled brake system according to an embodiment of the present invention includes a sleeve 1, a piston 3, an inlet check valve 5, an outlet check valve 8, and an orifice 10. Sleeve 1 is fixed to a pump housing and provides a working fluid passage in the inside thereof. Piston 3 is elastically supported in sleeve 1 by an inner spring 6, and allows the working fluid to flow into the inside thereof during the operation of the pump. Inlet check valve 5 is provided at the front end of piston 3 so as to discharge the working fluid into sleeve 1 by the pressure of the working fluid flowing into piston 3. Outlet check valve 8 is received in a cap 7 fixed to an end of sleeve 1, and opens or closes a discharge passage of sleeve 1. Orifice 10 is provided between sleeve 1 and the cap fixed to the end of the sleeve. Further, the orifice guides the working fluid discharged through the discharge passage of sleeve 1, which is opened by outlet check valve 8, to an outlet of the pump housing, and decreases a pulsating pressure of the working fluid that is caused by the reciprocation of piston 3.

Piston 3 is reciprocated by the drive of the pump, so that a working fluid flowing in the pump housing through an inlet of the pump housing passes through an inflow channel 2 of sleeve 1 and foreign substances are filtered by a filter. Then, the working fluid flows into the piston through an inflow channel 4 formed in piston 3.

Further, cap 7 is fixed to the end of sleeve 1. Cap 7 and orifice 10 form an outflow channel through which the working fluid discharged from sleeve 1 is discharged to the outlet of the pump housing.

Further, inlet check valve 5 includes a ball 5 a for blocking the outlet through which the working fluid flowing into piston 3 passes, a check valve spring 5 b that is fixed to the outlet of piston 3 and elastically supports ball 5 a, and a cover. The cover receives check valve spring 5 b, is fixed to piston 3, and has a radial channel serving as an outlet for the working fluid. However, as long as the working fluid is discharged from piston 3 at a constant pressure, the structure of the check valve may be modified in various ways.

Furthermore, outlet check valve 8 includes a ball 8 a that opens or closes the working fluid passage according to the contact between the ball and orifice 10 provided at the outlet of sleeve 1, and a check valve spring 8 b that is inserted into cap 7 so as to elastically support ball 8 a.

In addition, orifice 10 is fixed to the end of sleeve 1, and ball 8 a of outlet check valve 8 comes in close contact with the orifice so as to open or close the outlet of sleeve 1 according to the pressure that is applied to outlet check valve 8 provided in cap 7 by the working fluid provided in sleeve 1.

In this case, as being assembled, orifice 10 is centered on sleeve 1. This is achieved using the following structure. That is, orifice 10 is fitted to an orifice fixing end 1 a so that an axial center of orifice 10 naturally corresponds to the axial center of sleeve 1. The orifice fixing end is formed by cutting the end of sleeve 1 so that the end of the sleeve has stepped portions unlike the other portions.

The above-mentioned orifice 10 includes an annular body 11, fixation ends, and an outflow channel 17. Annular body 11 has a central hole 12, with which ball 8 a of outlet check valve 8 comes in close contact, at the center thereof. The fixation ends protrude from annular body 11 and are fitted to stepped orifice fixing end 1 a formed at the end of sleeve 1. Outflow channel 17 guides the working fluid, which is discharged from sleeve 1 through annular body 11, to the outlet of the pump housing.

Further, the orifice includes a plurality of fixation ends in order to increase a fixation force between the end of sleeve 1 and the fixation ends. That is, the fixation ends protrude from the annular body at three positions where annular body 11 is divided at an interval of 120° , so as to apply a reliable fixation force to the orifice fixing end 1 a of sleeve 1.

For example, the fixation ends are composed of an upper fixation end 14 and a pair of left and right lower fixation ends 13. Upper fixation end 14 is bent to protrude toward one side of annular body 11. The pair of left and right lower fixation ends 13 is bent to protrude toward one side of the annular body at positions corresponding to an angle of about 120° from upper fixation end 14.

When the orifice is fitted to sleeve 1, upper fixation end 14 and left and right lower fixation ends 13 corresponding to an angle of about 120° from the upper fixation end allow the axial center of the orifice to easily correspond to the axial center of the sleeve.

In addition, one of the fixation ends has an outflow channel 17 that guides the working fluid discharged from sleeve 1 to the outlet of the pump housing. For example, the outflow channel is formed in upper fixation end 14 that is positioned close to the outlet of the pump housing when the orifice is fitted to sleeve 1.

Upper fixation end 14 having outflow channel 17 is composed of left and right divided fixation ends 15 and 16. The left and right divided fixation ends has a gap therebetween, that is, the left and right divided fixation ends are separated from each other and are integrally formed with annular body 11 so that the working fluid can flow.

Further, outflow channel 17 includes an inlet 18 that is formed by cutting annular body 11 so as to allow the working fluid to flow, a narrow portion 19 that communicates with inlet 18 and decreases a flow width of the working fluid to increase the flow speed of the working fluid, an extension portion 20 that forms an end of narrow portion 19 and has a narrow width, and a wide portion 21 that expands at the end of extension portion 20.

In this case, wide portion 21 is formed in upper fixation end 14 of the fixation ends, and is formed by cutting upper fixation end 14 so that a distance between the facing surfaces of left and right divided fixation ends 15 and 16 is increased.

Furthermore, orifice 10 is integrally formed by pressing.

The operation of the pulsation pressure decreased type pump according to the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

According to the control valve of the present invention, when the working fluid is discharged from the oil pump driven by a motor on the basis of the operation of the electronically controlled brake system, the working fluid passes through annular orifice 10 provided at a position where the working fluid is discharged. Then, the working fluid flows to the outlet of the pump housing through outflow channel 17 formed in orifice 10. Accordingly, the pulsation superposition of the working fluid is decreased at the outlet due to piston 3 that is reciprocated by a cam, and a pulsating pressure generated at the outlet of the pump can be decreased from 20 bar to 5 bar or less.

The characteristic of the decrease in a pulsating pressure is caused by the operation of orifice 10 provided at the outlet of the pump. That is, orifice 10 is provided at the end of sleeve 1 surrounding piston 3 into which the working fluid flows so as to be positioned at a space formed between cap 7 having outlet check valve 8 and sleeve 1. Accordingly, the orifice forms a passage where the working fluid discharged from sleeve 1 passes through orifice 10 and then flows to outflow channel 17 of orifice 10.

In this case, orifice 10 is fixed to the end of the sleeve by using upper fixation end 14 and left and right lower fixation ends 13, which protrude from the annular body at positions where the annular body is divided at an interval of 120°. That is, when fixation ends 13 and 14 cover orifice fixing end la, which is formed by cutting the end of sleeve 1 so that the end of the sleeve has stepped portions, the central hole 12 of orifice 10 naturally corresponds to the axial center of sleeve 1.

The operation of orifice 10 will be described with reference to FIGS. 2A and 2B. The working fluid, which flows to the inlet of the pump housing due to piston 3 reciprocated by a cam when the pump is driven, passes through inflow channel 2 of sleeve 1, and foreign substances are filtered by a filter. Then, the working fluid flows into the piston through inflow channel 4 formed in piston 3.

Subsequently, inlet check valve 5 is opened by the pressure of the working fluid flowing into piston 3, so that the working fluid is discharged from piston 3 to sleeve 1. After that, the working fluid discharged to sleeve 1 applies pressure to outlet check valve 8, which is provided in cap 7 and blocks central hole 12 of orifice 10.

As the pressure is applied to outlet check valve 8 by the working fluid as described above, ball 8 a of outlet check valve 8 compresses spring 8 b and is pushed. As a result, a passage communicating with orifice 10 is opened.

Then, the working fluid in sleeve 1 passes through an outlet of opened orifice 10, that is, central hole 12 so as to be discharged from the sleeve. Since the working fluid passes through orifice 10 as described above, the amount and the flow of the working fluid are changed as compared to when the working fluid is directly discharged from sleeve 1 to a space between the sleeve and cap 7. As a result, the pulsation superposition is decreased.

As described above, the working fluid passing through the outlet of orifice 10, that is, central hole 12 flows into the space between sleeve 1 and cap 7. Then, the working fluid is discharged to the outlet of the pump housing along outflow channel 17 of orifice 10.

When the working fluid is collected at inlet 18 communicating with central hole 12 of orifice 10, the working fluid flows to narrow portion 19, which communicates with inlet 18 and has a narrow width, of outflow channel 17. Then, the working fluid passes through extension portion 20 that communicates with narrow portion 19 and has a narrow width, and wide portion 21. Subsequently, the working fluid is discharged to the outlet of the pump housing.

Each of narrow portion 19 and extension portion 20 have a narrower width than inlet 18. Accordingly, the narrow portion and the extension portion increase the flow speed of the working fluid flowing into the orifice, and wide portion 21 having a wide width increases the amount of the working fluid discharged from extension portion 20.

The reduction of the pulsation superposition of the working fluid in the pump depends on the shape and the hole of orifice 10. However, when the orifice is not provided, the pulsating pressure in the pump is experimentally 20 bar. When orifice 10 is provided, the pulsating pressure can be decreased to 5 bar at the maximum.

As described above, according to an embodiment of the present invention, when an oil pump, which is driven by a motor during the operation of an electronically controlled brake system, discharges a working fluid, an orifice for changing the amount and the flow of the working fluid is provided in the pump at a position where the working fluid is discharged. Accordingly, since the flow of the working fluid is changed by the orifice, the pulsation superposition generated at an outlet is significantly decreased and a pulsating pressure can be decreased to 5 bar or less at the maximum.

Further, according to an embodiment of the present invention, an orifice, which is provided in a pump at a position where a working fluid is discharged, is formed to have a simple shape by pressing. Therefore, it is possible to reduce machining time, inspection time, and manufacturing cost.

Furthermore, according to an embodiment of the present invention, a discharge channel is directly formed in an orifice that is provided in a pump at a position where the working fluid is discharged. In addition, the orifice is directly fixed to a sleeve. Therefore, a discharge channel does not need to be formed in a sleeve fixed to a cap, and the sleeve does not need to be machined for the assembling of the orifice. 

1. A pulsation pressure decreased type pump for a vehicle slip control system, comprising: a hollow sleeve that is fixed to a pump housing, receives a working fluid through an inflow channel formed in a radial direction, and includes a channel formed inside an end thereof opposite to the inflow channel; a piston that is elastically supported in the sleeve by an inner spring and is reciprocated by the drive of the pump so as to allow the working fluid to flow into an inflow channel communicating with the inflow channel of the sleeve; an inlet check valve including a ball that blocks an outlet through which the working fluid flowing into the piston passes, a check valve spring that is fixed to an outlet of the piston and elastically supports the ball, and a cover that receives the check valve spring, is fixed to the piston, and has a radial channel serving as an outlet for the working fluid; an outlet check valve including a ball that is received in a cap fixed to an end of the sleeve and opens or closes a passage of the working fluid discharged from the sleeve, and a check valve spring that is inserted into the cap so as to elastically support the ball; and an orifice that is provided between the sleeve and the cap fixed to the end of the sleeve and changes the flow of the working fluid discharged from the sleeve so as to decrease a pulsating pressure of the working fluid caused by the reciprocation of the piston, an outflow channel being integrally formed with the orifice so that the working fluid discharged from the sleeve through the outlet check valve is guided to an outlet of the pump housing.
 2. The pulsation pressure decreased type pump as defined in claim 1, wherein the orifice includes: an annular body that has a central hole, with which the ball of the outlet check valve comes in close contact, at the center thereof; fixation ends that protrude from the annular body and are fitted to a stepped orifice fixing end formed at the end of the sleeve; and an outflow channel that guides the working fluid, which is discharged from the sleeve through the annular body, to the outlet of the pump housing.
 3. The pulsation pressure decreased type pump as defined in claim 2, wherein a plurality of fixation ends is provided to the orifice in order to increase a fixation force between the end of the sleeve and the fixation ends.
 4. The pulsation pressure decreased type pump as defined in claim 3, wherein the fixation ends are formed in the annular body at three positions where the annular body is divided at an interval of 120°, so as to apply a reliable fixation force to the orifice fixing end of the sleeve.
 5. The pulsation pressure decreased type pump as defined in claim 3, wherein the fixation ends include an upper fixation end that is bent to protrude toward one side of the annular body, and a pair of left and right lower fixation ends that is bent to protrude toward one side of the annular body at positions corresponding to an angle of about 120° from the upper fixation end.
 6. The pulsation pressure decreased type pump as defined in claim 5, wherein left and right divided fixation ends, which are separated from each other and face each other, are formed by cutting a central portion of the upper fixation end so that an outflow channel for guiding the working fluid discharged from the sleeve to the outlet of the pump housing is formed in the upper fixation end.
 7. The pulsation pressure decreased type pump as defined in claim 2, wherein the outflow channel includes: an inlet that is formed by cutting the annular body so as to allow the working fluid to flow; a narrow portion that communicates with the inlet and decreases a flow width of the working fluid to increase the flow speed of the working fluid; an extension portion that forms an end of the narrow portion and has a narrow width; and a wide portion that expands at the end of the extension portion.
 8. The pulsation pressure decreased type pump as defined in claim 2, wherein the orifice is integrally formed by pressing. 